BOSTON -- Republican Scott Brown dealt a devastating blow to President Obama's domestic agenda Tuesday night by capturing the Senate seat of the late Edward M. Kennedy, the legendary Democrat who had made health-care reform the cause of his political career.

Brown, a little-known Massachusetts state senator 10 days ago, won the special election by running directly against the health-care legislation that Kennedy trumpeted before his August death and that Obama considers his most important legislative priority. Coming on the eve of the first anniversary of Obama's historic inauguration, the stunning upset eliminated the Democrats' filibuster-proof majority in the Senate and created an immediate roadblock to approving the health-care plan and other Obama priorities.

The symbolism of the rejection was difficult to overstate: Kennedy, who held his Senate seat for nearly 47 years, served as a political mentor to Obama and was the patriarch of the Kennedy family's political dynasty. Even before the polls closed at 8 p.m., Obama's top advisers engaged in a public blame game with the campaign of state Attorney General Martha Coakley, the Democratic candidate, over who is responsible for the crippling setback to the party.

Brown's late surge was fueled by voter anger about the high unemployment rate and by his vow to block the president's proposal for health-care reform. He drew chants of "41!" during his acceptance speech Tuesday night, symbolic of his role as the 41st member of the Senate GOPcaucus.

"This Senate seat belongs to no one person, to no political party. . . . This is the people's seat," Brown said after an election that drew more than 2 million voters. It was the first U.S. Senate win for a Republican in Massachusetts since 1972.

Coakley's campaign criticized the national Democratic establishment, saying that it did not do enough to help raise money and that it underestimated how sour the political environment had become for Democrats even in traditionally blue states.

"Money was the issue after the primary. We just couldn't get people's attention," state Senate President Therese Murray (D), one of Coakley's leading supporters, said Monday at the candidate's final campaign stop, an Irish pub just south of Boston. Murray said the campaign held a "come-to-Jesus meeting" on Jan. 4, just as a public poll was released showing Brown closing in, and only then did the financial spigots begin to open up for Coakley.

Obama aides and leading party strategists rejected Coakley's complaints as revisionist history, saying she was too late in alerting them to the perilous state of her campaign. By then, Brown's campaign had taken off, as conservatives nationwide saw a chance to defeat Obama's agenda and deposited more than $5 million into Brown's coffers in the final 10 days of the race, according to estimates.

Eventually, the Democratic Senatorial Campaign Committee and the Democratic National Committee poured more than $2 million into the state and dispatched a wave of party operatives, who essentially took over her effort. Obama traveled to Boston on Sunday afternoon to try to rally a liberal base that had been lulled into complacency by a campaign that appeared to take victory for granted after winning the Dec. 8 primary.

"The White House did everything we were asked to do," White House senior adviser David Axelrod said before the polls closed Tuesday. "I think if we had been asked earlier, we would have responded earlier."

Crediting Brown with "a very clever campaign," Axelrod added: "As a practitioner in politics, my hat's off to him."

After Coakley conceded Tuesday, White House press secretary Robert Gibbs issued a statement in which Obama congratulated Brown and said he "looks forward to working with him the urgent economic challenges facing Massachusetts families and struggling families across our nation."

Risky options

Brown's victory immediately threw into chaos the delicate health-care negotiations Obama oversaw last week at the White House, as Democratic congressional leaders inched closer to a final deal that could clear both chambers. That path was predicated on having a 60-member Democratic caucus in the Senate. Democrats have several politically risky options in the aftermath of Brown's victory, but House Speaker Nancy Pelosi (D-Calif.) had declined to endorse any of those choices.

After the results became clear, Pelosi convened a meeting of her leadership team late Tuesday to discuss next steps, aides said.

Republicans hailed Brown's upstart campaign -- which began with the longtime politician playing the role of everyman by driving his pickup truck across Massachusetts -- as a signal that substantial gains could be coming for the GOP in the November midterm elections. Independent voters, who represent half of the state's electorate and have long favored Democrats in Congress, appeared to break in Brown's favor in the final days, according to public polls.

Brown, who will serve the remaining three years of Kennedy's term and face reelection in 2012, won the votes of women such as Jaimee Vassallo, 52, a teacher who is registered without a party affiliation. Entering her polling place in Wilmington, she grabbed the arm of a friend and staggered, half comically, at the prospect.

"Oh, Mary, I'm switching over to the Republican side for the first time ever," Vassallo said. "It's a tough day."

Republicans said Brown's staunch opposition to the health-care legislation could serve as a road map for other Republicans in the fall, arguing that Democrats had badly misread the electorate after their huge victories in 2006 and 2008. "The voters in Massachusetts, like Americans everywhere, have made it abundantly clear where they stand on health care. They don't want this bill and want Washington to listen to them," Senate Minority Leader Mitch McConnell (Ky.) said in a statement.

Alex Vogel, a GOP strategist, said the White House was right in dismissing Coakley as a "bad candidate."

"But that alone doesn't explain losing Ted Kennedy's Senate seat mere months after his death," Vogel said. "President Obama won the state by 26 points, and the entire congressional delegation is Democratic. What the Brown success tells me is that the electorate did not leave the Bush years liberalized; they left angry with bad and ineffective government."

Problems for reform

The Democratic infighting was an amplification of the postmortems that followed the November gubernatorial defeats for Democrats in Virginia and New Jersey, losses that White House strategists suggested were related to local factors and ineffective candidates, not the national environment. But the loss of Kennedy's seat -- Democrats turned the week-long memorial after his August death into a veritable pep rally for health-care legislation -- will be harder to dismiss.

The legislative quagmire of health-care reform, which has consumed Congress since July 4, has left Democrats unable to unite on a new economic program. In an interview Sunday, Coakley said voters' top concerns are employment and the economy, but her standard stump speech included no new proposal for creating jobs. Nor did Obama's speech Sunday offer any specifics for promoting job creation, rather warning that every other aspect of his domestic agenda, from new regulations on Wall Street to climate-change legislation, could be in jeopardy after Brown's win.

After initially suggesting that it would take up to 15 days to certify the victor -- possibly giving Democrats time to pass health-care legislation with the vote of Sen. Paul Kirk (D), who was given the temporary appointment to fill Kennedy's seat until the special election was held -- Massachusetts Secretary of State William F. Galvin said Tuesday that he would probably certify a victor immediately if the outcome were clear.

Kane reported from Boston and Washington, Vick from Boston and Wilmington. Staff writer Michael D. Shear in Washington contributed to this report.